The objectives of this proposal are to determine whether a certain dietary component, specifically L-tryptophan, may act as an inhibitor and/or a promoter in chemical carcinogenesis. Chemical carcinogens such as diethylnitrosamine, N-2-fluorenylacetamide, ethionine, and 3'-methyl-dimethylaminoazobenzene will be used. The effects of feeding purified diets containing single chemical carcinogens and elevated levels (1%) of L-tryptophan will be determined. Livers and urinary bladder will be evaluated for tumorigenesis and for selected enzyme changes.